## 43.5. Redirection in C Shell: Capture Errors, Too?

The `>` (right angle bracket) operator redirects the standard output of a process to a file. It doesn't affect the standard error. If you're logged in and can see any messages written to standard error, that's okay:

>     % nroff -ms report.ms > report.out &
>     [1] 10316
>        ...Later...
>     nroff: can't open file /hoem/jpeek/report.data

But if you log out and leave the job running, you'll never see those errors unless you use the csh operator `>&`. It redirects both standard output and standard error to a file. For example:

`make` Section 11.10

>     % make >& make.output &
>     [1] 10329
>     % logout
>        ...Later...
>     % cat make.output
>             cc -O -c random.c
>             cc -O -c output.c
>     "output.c", line 46: syntax error
>     "output.c", line 50: time_e undefined
>     "output.c", line 50: syntax error
>        ...

You might also use the `>&` operator while you're logged in and watch the output file with tail -f (Section 12.10). If you don't want the errors mixed with other output, you can split them to two files; see Section 43.1.

The C shell also has a pipe operator, `|&`, that redirects both standard output and standard error. It's great for running a job in the background or on another computer and mailing (Section 1.21) any output to me:

>     % make |& mailx -s "'make bigprog' output" jpeek@jpeek.com &
>     [1] 29182 29183

If I'd used plain `|` instead of `|&`, any text on the standard error wouldn't go into the mail message.

-- JP

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